This invention relates to audio speakers, and more particularly to a mechanism for removing heat from such speakers.
Driving an audio speaker above its rated power for a short period of time, or near its rated power for an extended period, in order for example to achieve high volume output, can result in overheating of the voice coil of the speaker which can adversely affect performance of the speaker and can cause damage, both to the voice coil and to other adjacent components. Such damage can require either expensive repairs or replacement of the speaker. While heavier duty voice coils can be used, this does not deal with potential thermal damage to other components of the speaker, and will generally result in greater heating of these other components. Heavier duty voice coils can also adversely affect response and other performance parameters of the speaker.
To overcome these problems, various techniques have been utilized in the past to either actively or passively cool the voice coil and other components of a speaker. Active cooling, generally involving the use of one or more fans, is expensive, requires a reasonable amount of space, and may introduce undesired background noise. Such cooling is therefore generally utilized only for large commercial applications and is not suitable for use in home or auto applications. Past attempts to introduce passive cooling to audio speakers have generally involved either mounting heat sinks to an existing component of the speaker drive mechanism, for example to the base plate, and/or arrangements to use movement of the speaker cone and/or spider to move air over the voice coil and other components of the speaker to be cooled, to some component of the speaker which can sink heat from such air. These efforts have met with varying degrees of success, frequently at a significant cost in speaker redesign, but many of these approaches have not been able to pass the heated air over a sufficient heat sink area to achieve significant cooling benefits. Further, many of these prior art approaches have relied on only a single mode of cooling, for example radiant cooling, and have therefore been less effective in cooling the speaker then if multiple cooling modes were utilized.
Further, air being moved through various parts of a speaker, and in particular over the voice coil thereof, can result in air turbulence which produces significant audible air noise. The extent to which this noise is objectionable is exacerbated when the speaker is mounted with its magnets and voice coil facing out of the enclosure, an arrangement which is becoming increasingly popular in automotive applications in order to enhance convection cooling of the speaker drive mechanism.
A need therefore exists for an improved cooling mechanism for an audio speaker which passively cools the voice coil and other components of the speaker utilizing multiple cooling modes with minimum added hardware, minimum added cost, negligible (if any) air turbulence (and thus substantially no audible air noise) and a significantly larger heat sink area over which heated air is passed than has generally been achieved in prior art mechanism.
In accordance with the above, this invention provides a cooling mechanism for an audio speaker of the type having a drive mechanism, a voice coil, and a basket over the drive mechanism, the basket having a spider and/or a speaker cone mounted therein, movement of the spider and speaker cone being controlled by the voice coil. The cooling mechanism includes a vent plate of a thermally conductive material mounted between the basket and the drive mechanism and extending around the voice coil, the vent plate having a plurality of radial vents, each of which vents extends from inside the plate adjacent the voice coil to the outside of the speaker. The thermally conductive material of the vent plate is preferably on at least three sides of each vent. A filter is preferably included in each vent to limit material flowing into the speaker through the vents, the filter preferably being a substantially cylindrical filter fitted in a circumferential groove formed in the vent plate between the inside and outside thereof. The drive mechanism normally includes top and bottom plates with at least one magnet therebetween, the top plate and magnets each being of a selected width, and the vents being of a length which is in substantially the same value range as such selected width. The vent plate is preferably dimensioned to be mounted closely adjacent the voice coil so as to facilitate radiant cooling of the coil. The vent plates are also designed to permit air flow therethrough with negligible air turbulence. In particular, all comers of the vent plate around which air flows are rounded and each vent has sufficient cross-sectional area to prevent turbulence of air flowing therethrough.
The vent plate is preferably a flat cylindrical housing of a thermally conductive material which housing has a hollow center portion in which the voice coil fits. The plurality of radial vents are formed in the housing extending from the hollow center portion to an outer wall of the housing, each of the vents having thermally conductive material of the housing on at least three sides thereof. The vent plate preferably includes a structure for receiving a filter for each vent which structure is, for a preferred embodiment, a circumferential groove formed in the housing between the center portion thereof and the outer wall. The hollow center portion of the vent plate is preferably dimensioned so that the vent plate is mounted closely adjacent the voice coil to facilitate radial cooling thereof and the vent plate is preferably designed so as to permit air flow therethrough with negligible air turbulence. As indicated above, such design includes all comers of the vent plate around which air flows being rounded and each vent having a sufficient cross-sectional area to prevent turbulence of air flowing therethrough.
In some applications a solid plate of a thermally conductive material may be substituted for the preferred vent plate, the solid plate being mounted between the drive mechanism and the basket, surrounding the voice coil, and being closely spaced therefrom.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings, the same reference numerals being used for common elements in each of the drawings.